Interpretive Summary: White button, crimini, shiitake, maitake, enoki, oyster, chanterelle, morel, portabella, and uv-treated portabella mushrooms were sampled from U.S. retail outlets and major producers. These mushrooms were analyzed for three naturally occurring forms of the vitamin folate by a validated analytical method. Four samples of each product, plus a mushroom sample with known folate content and a reference material, were analyzed. Chanterelle and morel varieties had the lowest total folate content(2-6 ug/100g), the oyster variety had the highest (44.2 µg/100g), and other varieties contained from 12.4 µg/100g (shiitake) to 29.8 µg/100g (vitamin-D-enhanced portabella). Enoki and oyster had almost exclusively one form of the vitamin. Morel and chanterelle contained predominately the other two forms. the other varieties tsted had similar amounts of the three folates. Enoki, oyster, and shiitake, unlike all others, had low to non-detectable levels of one form. Values for total folate will be released in the USDA National Nutrient Database for Standard Reference and can be access on the web. These precise data on the composition of the three forms of folate in different types of mushrooms will facilitate assessment of the dietary contribution of naturally occurring folate to total folate intake.

Technical Abstract:
White button, crimini, shiitake, maitake, enoki, oyster, chanterelle, morel, portabella, and uv-treated portabella mushrooms were sampled from U.S. retail outlets and major producers. Folate (5-methyltetrahydrofolate [5MTHF], 10-formyl folate [10FF], 5-formyltetrahydrofolate [5FTHF]) was analyzed using a validated LC-MS method in four composites of each product, including an in-house mushroom control composite and a reference material (BCR 485 Lyophilized Mixed Vegetables). Chanterelle and morel had the lowest total folate (2-6 ug/100g), oyster had the highest (mean, 44.2 µg/100g), and the other varieties tested contained 12.4 µg/100g (shiitake) to 29.8 µg/100g (vitamin-D-enhanced portabella) total folate. Enoki and oyster had almost exclusively 5MTHF. Morel and chanterelle contained predominately formyl folates. Other species had similar amounts of 5MTHF and formyl folates. Enoki, oyster, and shiitake, unlike all others, had low to non-detectable 10FF (<1 µg/100g). These precise data on the composition of folate vitamers in different types of mushrooms will facilitate assessment of the dietary contribution of naturally occurring folate to total folate intake.